Effect of topography on spatiotemporal patterns of soil moisture in a mountainous region of Northwest China

Abstract

Soil moisture data were obtained from the Watershed Allied Telemetry Experimental Research Network (Waternet), located in a mountainous region of northwest China, to evaluate the impacts of environmental factors on regional soil moisture spatiotemporal patterns. Based on the temporal stability analysis method, the results showed that soil moisture spatial distributions in the study region were more correlated with elevation (a local control) than with precipitation (a regional control), highlighting the importance of local factors in controlling regional soil moisture spatial patterns. Moreover, the spatial variance of the absolute soil moisture content (e.g., the total soil moisture spatial variability) at the Waternet stations was decomposed into time-invariant and time-variant components. The results showed that the spatial variability in the time-invariant component (e.g., the temporal average soil moisture content) was the primary component in the total soil moisture spatial variability. More importantly, the temporal evolutions of the time-variant components and their contributions to the total soil moisture spatial variance were also affected by local factors, particularly by elevation in the study region. Overall, this study provides further observational evidence, which suggests that depending on specific regional conditions, local factors through affecting both time-invariant and time-variant components can outweigh regional factors in controlling soil moisture spatial variability at regional scales.